Rotary hearth furnace

ABSTRACT

A rotary hearth furnace comprising a single, unitary heating chamber the rotatable hearth of which is provided with a plurality of openings to receive turntables which are also rotatable, each turntable having a spindle to receive a coil or coils of rod. The furnace is provided with a charging station having a lift mechanism which is movable from a retracted position beneath the hearth into engagement with a properly positioned turntable so as to enable the turntable to be raised out of contact with the hearth framework so that a coil may be deposited on the turntable about the spindle without putting undue strain on the hearth framework. The lift mechanism is capable of raising the turntable high enough above the hearth so that, when desired, the mechanism which is used normally to charge the coil of rod onto the turntable may be used to remove the turntable from the furnace. The furnace is also provided with an unreeling station having both a lift mechanism and a turntable rotating mechanism, all of which is movable from a retracted position beneath the hearth to an elevated position so as to move a turntable from contact with the hearth framework so that the rotating mechanism may be actuated to rotate that turntable in either direction as desired. This lift mechanism may raise this turntable to a more elevated position to enable any debris collecting between the turntable and the heath to be cleared. An indexing mechanism is provided which moves the hearth and its turntables in a step by step fashion. Preferably the furnace is gas fired through burners located about the ceiling thereof.

United States Patent 1m Lowderman et al.

[ ROTARY HEARTH FURNACE [75] Inventors: Ernest W. Lowderman,

Independence; Leland L. Barrington, Overland Park; Ferdinand Young, Jr.,Independence, all of Mo.

[73] Assignee: Armco Steel Corporation,

Middletown, Ohio [22] Filed: Feb. 4, 1974 [2]] Appl. No.: 439,411

Related U.S. Application Data [62] Division of Ser. No. 297.886, Oct.16, 1972, Pat. No.

Primary Examiner-John J. Camby Attorney, Agent. or Firm-Melville,Strasser, Foster & Hoffman [451 May 13,1975

[57] ABSTRACT A rotary hearth furnace comprising a single, unitaryheating chamber the rotatable hearth of which is provided with aplurality of openings to receive turntables which are also rotatable,each turntable having a spindle to receive a coil or coils of rod. Thefurnace is provided with a charging station having a lift mechanismwhich is movable from a retracted position beneath the hearth intoengagement with a properly positioned turntable so as to enable theturntable to be raised out of contact with the hearth framework so thata coil may be deposited on the turntable about the spindle withoutputting undue strain on the hearth framework. The lift mechanism iscapable of raising the turntable high enough above the hearth so that,when desired. the mechanism which is used normally to charge the coil ofrod onto the turntable may be used to remove the turntable from thefurnace. The furnace is also provided with an unreeling station havingboth a lift mechanism and a turntable rotating mechanism, all of whichis movable from a retracted position beneath the hearth to an elevatedposition so as to move a turntable from contact with the hearthframework so that the rotating mechanism may be actuated to rotate thatturntable in either direction as desired. This lift mechanism may raisethis turntable to a more elevated position to enable any debriscollecting between the turntable and the heath to be cleared. Anindexing mechanism is provided which moves the hearth and its turntablesin a step by step fashion. Preferably the furnace is gas fired throughburners located about the ceiling thereof.

16 Claims, 12 Drawing Figures PATENTED RAY I 31875 SHEET &0? 8

ROTARY HEARTH FURNACE CROSS REFERENCE TO RELATED APPLICATION Thisapplication is a division of copending application Ser. No. 297,886filed Oct. 16, l972, in the names of the same inventors and entitledROTARY HEARTH FURNACE AND SYSTEM FOR FORMING BALLS, now U.S. Pat. No.3,827,267.

BACKGROUND OF THE INVENTION 1. Field of the Invention The furnace ofthis invention, although capable of many uses, has particular utilitywhen used as a part of the system for feeding hot rod in a substantiallycontinuous manner to forging apparatus for forging steel balls for usein grinding mills. A typical forging apparatus is shown in U.S. Pat.3,239,912 and 3,478,556 to Baumgartner et al. The halls coming from suchforging apparatus are then shaped into a substantially true sphere by apancake sizer such as is shown in U.S. Pat. 3,621,692 to Weed.

The forging apparatus above noted is too fast to feed with hot bars iffull and proper utilization of the apparatus is to be realized. It wasdetermined, therefore, that best utilization of the forging apparatuscould be achieved if hot coils could be used for feeding the apparatus.The rotary hearth furnace of this invention provides the means by whicha succession of coils of rod may be properly heated and then fed almostcontinuously into the forging apparatus.

2. Description of the Prior Art Although a search of the prior art wasconducted in an effort to locate those United States patents mostpertinent to the development at hand, no assertion is made that the bestsuch art was located, this, however, being the intent of the search;such search developed the following U.S. Pat. Nos: 3l0,402 Fox, 734,114Beker, 1,903,909 Cope, 2,413,228 Hepburn, 2,401,930 Hansen, 201,582Wilmsmann, 373,463 Lenox, 444,55! Daniels, and l,l 18,869 Kugel.

Fox discloses a rotary annealing cylinder with a plurality of rotatableannealing boxes thereon. Beker discloses a furnace having a plurality ofindividual, separately heated, heating chambers, each chamber having asingle rotatable support for a coil of rod. Cope discloses a rotaryhearth with a plurality of containers for holding material to betreated, each container, however, being non-rotatable. Hepburn disclosesa furnace the lower half of which, carrying fixed retorts, rotates.Hansen discloses step by step rotation of a carrier having a pluralityof rotating heads thereon. The remaining patents developed by the searchdo not seem to be of particular significance.

SUMMARY OF THE INVENTION The furnace of this invention is a part of asystem which enables optimum use of the forging and sizing apparatusabove identified so that a succession of steel balls may be formedalmost continuously from coiled rod of suitable material. The furnacecomprises a sin gle, unitary heating compartment completely lined withrefractory material. The refractory material comprising the furnacehearth is supported by suitable framework. A plurality of evenly spacedopenings are provided in the hearth and each such opening is providedwith a turntable which rests within the opening, out of contact with thehearth but supported on portions of that framework which also supportsthe hearth. Each such turntable is provided with a spindle about whichone or more coils of rod may be deposited.

Operation may begin with a first turntable being lo cated in chargingposition, the furnace door being opened and a coil of rod beingdeposited on the so located turntable by the charger which is in turnfed by a suitable coil conveyor. The hearth is indexed so that the firstturntable so charged is eventually brought to the unreeling station. Inthe meantime, other coils of rod are placed on the various turntableswhen positioned before the charger. The timing will be such that by thetime the first coil travels from the charging station to the unreelingstation, it will be hot enough to be fed into the forging apparatus.Each succeeding coil will also be sufficiently heated by the time it isfed into such forging apparatus, the hearth having been indexed therequired number of times to bring such succeeding coil into position forunreeling into the forging apparatus.

The grinding ball sizer is in line with the forging apparatus to finishthe shaping of the balls. The rotary hearth is continually indexed andthe operation proceeds as stated above. New coils are loaded on an emptyturntable at the loading or charging station while a feeding orunreeling operation is taking place.

The turntable positions at the charging-loading and feeding-unreelingstations have power means which rise to engage the turntablesv At thecharging station there is two position lifting, the first position beingto stabilize the turntable and remove it from contact with the hearthframe structure while the coil of rod is deposited on such turntable,and the second position is to lift the turntable even higher so that theone piece spindle-turntable can be replaced when necessary. At theunreeling station, the power means lifts to engage the turntable then inposition and to effect a rotating action to feed the coil to theoperator who then feeds the coil into the forging apparatus. The powerto rotate the turntable is disengaged once the coil is fed into theforging apparatus as this latter apparatus will then pull the coilitself. The turntable power means can act as a slight drag on the coilto create a small amount of desired back tension. The power means mayalso be actuated to lift the turntable to a higher position to enabledebris to be cleaned from between such table and the hearth proper.

The furnace is gas fired by a plurality of jets evenly disposed aboutthe ceiling of the furnace. The furnace chamber is evenly heated todesired temperature by these jets and there are no internal partitionsseparating the turntables and the coils of rod located thereon one fromanother. The gas fired furnace normally operates slightly aboveatmospheric pressure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic plan view ofthe rotary hearth furnace and system for forming balls from coils ofsuitable rod material.

FIG. 2 is a cutaway perspective view of the rotary hearth furnace ofthis invention.

FIG. 3 is a sectional view taken along the line 33 of FIG. 1.

FIG. 4 is a diagrammatic plan view indicating the position of thefurnace hearth supports and of the indexing mechanism.

FIG. 5 is an enlarged elevational view, partly in section and partlybroken away, taken on the line 5-5 of FIG. 4.

FIGS. 6, 7 and 8 are elevational views of the power means which engagesthe turntable when positioned at the unreeling station.

FIGS. 9, l0 and 11 are elevational views of the power means for engaginga turntable when positioned at the charging station.

FIG. 12 is an enlarged sectional view taken on the line 12-12 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, therotary hearth furnace and system for forming balls is generallyillustrated. The rotary hearth furnace is indicated at 20, the coilloader at 21, the coil conveyor at 22, the forging apparatus at 23, thegrinding ball sizer at 24 and the mechanical and gravity conveyors forremoving the finished balls to storage and the like at 25a and 25b. Theforging apparatus may be like that shown in the Baumgartner et al U.S.Pat. Nos. 3,239,912 and 3,478,556 and, therefore, will not be describedin greater detail here. Similarly, the grinding ball sizer 24 may belike that shown in the patent to Weed U.S. Pat. No. 3,621,692 andfurther description will not be set forth herein. A turntable 26a and aball conveyor 26b transfer the forged balls from the forging apparatus23 to the finishing sizer 24. The coil conveyor 22 delivers coils ofcold rod to the charger 27 which periodically deposits one or more coilsof rod on a turntable positioned at the charging station. For purposesof illustration the center of the charging station is indicated at 28and the center of the unreeling station at 29.

In FIG. 1 the rotary hearth furnace is seen in top plan with theplumbing removed. Ten turntables 30 having spindles 31 are uniformlydisposed about the furnace hearth. No coil of rod has yet been placed onthe turntable 30 which is at the charging station 28. A coil of rod 32is on that turntable 30 which is located at the unreeling station 29.Normally there will be no coil of rod on the single turntable locatedbetween the unreeling station 29 and charging station 28, noting thatrotation of the hearth is in a counterclockwise direction as viewed inthis FIG. 1. The remaining seven turntables 30 are all shown as having acoil of rod 32 mounted thereon.

The pairs of openings 33a and 33b schematically represent the gas firedjets by which the interior of the furnace is heated, these jets beinglocated in the ceiling of the furnace, discharging thereinto, and beingsuitably fed with conventional gases through conventional plumbing (notshown) as will be understood by those skilled in the art. Although apair of such burners 33a and 33b may be positioned for each of the tenturntables, it may be desirable to omit one or more of these at thatposition wherein the turntable is normally empty, that being theposition to which the hearth is indexed immediately after a coil of rodhas been unreeled from the station 29 and fed into the forging apparatus23.

Coils of rod of suitable material are placed on the coil loader 2] andthereby transferred to the coil conveyor 22. This conveyor is designedto lift the coil, actually a succession of coils, and move it to thecharger 27, thereafter lowering to thereby deposit the coil on suchcharger. The charger is designed to move into the charging station 28and deposit the coil on that turntable 30 then positioned there, aboutthe spindle 31. The furnace door 34 is located at this charging stationand will, of course, be raised before the coil is charged into thefurnace. After the charger 27 retracts, the door 34 will be closed, andthe indexing mechanism will bring the next turntable into position, thehearth being moved in a counterclockwise direction, as viewed in FIG. 1,to accomplish this. By the time the first coil charged into the furnacereaches the unreeling station 29, nine of the ten turntables will carrysuch coils, that coil located at the unreeling station now beingproperly heated and ready for feeding into the forging apparatus 23.This latter step is accomplished by an operator, aided by mechanism tobe described, grabbing an end of the coil with suitable tongs andfeeding it to the known receiving mechanism of the forging apparatus 23.This forging apparatus will pull the hot coil of rod therethrough,forming grinding balls which are then transferred by turntable 26a andconveyor 26b to the grinding ball sizer 24 which will finish them andsend them on their way to storage by means of the mechanical conveyor25a and the gravity conveyor 25b. As soon as the first turntable toreach the unreeling station is relieved of its coiled rod in thismanner, the hearth will be indexed to bring the next turntable intoposition for immediate feeding of its coiled rod to the forgingapparatus 23 while an additional coil is placed on the previously emptyturntable 30 when moved into position before the charger 27. Thisoperation will continue in this manner so long as it is desired tomanufacture finished grinding balls.

Referring now to FIGS. 2, 3, 4 and 12, certain of the features of therotary hearth furnace 20 will be described in greater detail. As isindicated in these figures, the walls 35, including also the ceiling andthe rotary hearth or floor 36, are made of or lined with refractorymaterial, as will be understood by those skilled in the art. Withrespect to the hearth 36, it includes a steel plate 37 attached tosuitable frame members generally indicated at 38. As perhaps best seenin FIGS. 3 and 12, the frame structure 37-38 includes a first, annularouter rail 39 attached thereto and from which depends a second, annularouter rail 40 having a member 41 which engages a plurality of rollers 42suitably supported in bearings 43 disposed on a building floor beneaththe hearth 36. Similarly, there is a first annular inner rail 44 fixedto the frame structure 37-38 and a second annular, inner rail 45depending from the rail 44 and having a member 46 resting on a pluralityof rollers 47 suitably supported in bearings 48 placed about thebuilding floor beneath the hearth. In this manner the reinforced hearth36 is supported on the plurality of rollers 42 and 47.

FIG. 4 diagrammatically represents more detail respecting the locationof the rollers and bearings 42, 43 and 47, 48. These support rollers orwheels 42 are designed to be engaged by the rail members or outer tracks39-41 while the support rollers or wheels 47 are designed to be engagedby the inner rail or track members 44-46. Also spaced about theunderside of the hearth frame structure are a plurality of trackstabilizing wheels 49 and 50 for the outer and inner tracksrespectively. The unreeling pit, in which the lifting mechanism, to bedescribed, is located is shown at 290 in FIG. 4, and the charging pitfor housing its lifting mechanism, to be described, is indicated at2821. A plurality of frame members 51 are diagrammatically shown in FIG.4 as constituting a part of the understructure supporting the plate 37and hearth 36. The indexing means, to be described in detail inconnection with the description of FIG. 5, is generally indicated at 52in FIG. 4. A circular indexing rail will be fastened to the underside ofthe hearth frame structure, as will be described in connection with FIG.5.

Referring now to FIGS. 2 and 3, other features of the rotary hearthconstruction will be described. The right hand side of FIG. 3 depicts aportion of the charging station 28 while the left hand side of FIG. 3depicts a portion of the unreeling station 29. The lift mechanisms forboth stations have been omitted; these are shown, and will be describedlater, in FIGS. 9 through I] and 6 through 8 respectively. Theturntables 30 normally rest on the frame structure 37-43, 44-48 andvarious of the web members 51. Openings 53, therefore, are provided inthe hearth 36 and these openings are of greater diameter than those ofthe turntables 30. This insures that, even in the down position whereinthe turntable is resting on the frame structure, the turntables 30 willnot be in direct contact with the hearth 36. This prevents damage to thehearth and to the turntables which might otherwise occur should therefractory materials of which each is made come into contact with oneanother. The turntable 30 at the charging station 28, as shown in FIG.3, is in its normal, down position wherein it is resting on the framestructure while the turntable 30 at the unreeling station 29 is shown,in FIG. 3, in its unreeling position wherein it has been lifted, bymechanism to be described but not shown in FIG. 3, off the framestructure.

Referring now to FIG. 5, the indexing mechanism for rotating the hearth36 will be described. This mecha nism 52 includes brace structure 54mounted on the building floor. Connected to the structure 54 is apiston-cylinder arrangement 55. Pivotally connected to thepiston-cylinder arrangement 55, as indicated at 56, is a carriage 57having a spring biased dog 58 mounted thereon. The dog 58 is normallybiased to the position shown in FIG. 5. An indexing rail 59 havingflanges 60 is suitably secured to the frame understructure generallyindicated at 38a. The carriage 57 is supported from this indexing rail59 by pairs of rollers 61 and 62 which ride on the flanges 60 on eitherside of the rail 59. These rollers 61 and rollers 62 are mounted onbracket members 63 and 64, respectively, connected to the carriage 57.The underside of the rail is provided with a series of dogs 65 spacedcompletely around the hearth. The dogs 65 are arranged to be engaged bythe carriage dog 58.

Upon actuation of the piston-cylinder arrangement 55, by control meansnot shown, but in such manner as will be readily understood to thoseskilled in the art, the carriage 57 advances and the dog 58 engages adog 65 whereby the frame structure and hearth will be moved the lengthof the piston stroke. When the piston is retracted, the dog 58, beingspring biased, will pass beneath the next dog 65 to the rear of thatinitally en gaged whereupon further actuation of the piston will resultin the dog 58 engaging such next dog 65 to again advance the hearth.Depending on the size of the furnace, the number of turntables andsimilar dimensions of the piston cylinder and spacing of the variousdogs, one or more actuations of the piston-cylinder 55 may be requiredto index the hearth so as to move the various turntables from oneposition to the next.

Turning again to FIG. 12, mechanical means are illustrated for sealingthe rotary hearth furnace. As shown, an L-shaped bracket 66 is securedto the frame structure 38. A similar L-shapcd bracket 67 having anupturned portion 68 is secured to the stationary furnace wall 35 asindicated at 69. A .l-shaped member 70 has a downwardly turned portion71 which hooks over the upturned portion 68 of the member 67. As thehearth 36 is indexed within the confines of the stationary furnace wall35 by the mechanism described in connection with FIG. 5 and generallyindicated in FIG. 4, the member 66 will slide along the members 70 whosehinging action from fulcrums at 68 permits movement to allow for heatexpansion and the escape of debris, especially scale. Also of importanceis that the furnace is sealed from undue loss of heat.

FIGS. 6, 7 and 8 disclose lift mechanism generally indicated at 72 forthe turntable 30 when located at the unreeling station 29.

This mechanism includes a supporting platform 73 having an upstandingnose 74 located centrally thereof. This nose is designed to registerwithin a corresponding opening located in the center of the lower partof each of the turntables 30, such an opening being indicated at 75 inthe left hand side of FIG. 3. The platform 73 rests on bearings 76located on a member 77 which is supported from a first table member 78by a plurality of braces 79. Suitably supported from the first tablemember 78 is a reversible motor 80 the output end of which is connectedby a belt or chain and sprockets 81 to suitable pulley mechanism 82.This mechanism drives, by conventional means not shown but generallylocated within the housing 83, a shaft 84 connected to the platform 73.Actuation of the motor 80 may rotate the platform 73 in either directionas desired.

The mechanism 72 includes a first set of cylinders 85 having pistons 86movable therein by conventional means, as will be understood by thoseskilled in the art. A second table member 87 is secured to the ends ofthe pistons 86. A second set of cylinders 85a is secured to the bottomof the table member 87 and is provided with pistons 88 which areconnected to the first table member 78.

The platform 73 and associated mechanism is shown in its retractedposition in FIG. 6 at which time it will be understood that themechanism 73-74 is beneath and out of the way of the frame structureconnected to the underside of the hearth 36. The lift mechanism 72 isdesigned to permit upward movement of the platform 73 by successiveincrements to two positions. When the pistons 86 are actuated, thetables 78 and 87 are moved to a first position wherein the platformpasses upwardly through the hearth frame structure, through the open ing53 of the hearth floor 36 and into contact with the underside structureof that turntable 30 then located within the unreeling station 29 so asto move the turntable off of the hearth frame structure a shortdistance. The turntable 30 and coil 32 (see FIG. 2) of rod material willthen be supported solely by the platform 73 and the related mechanismgenerally indicated at 72. At this first position it is possible torotate the platform 73 in either direction by actuation of thereversible motor 80. This will enable an operator to so position thecoil 32 that he can grab the end thereof by a pair of tongs insertedthrough a small door so as to pull the end out of the furnace and intothe forging apparatus 23. After the end of the rod 32 is engaged withinthe forging apparatus 23, clutch mechanism, not shown, for the motormechanism 8084 may be released whereafter such turntable power means80-84 may be used as a slight drag on the coil to create a small amountof desired back tension as the coil is fed into the forging apparatus.The position of the tables 78 and 87 after upward extension of thepistons 86 is illustrated in FIG. 7. At this point the nose 74 hasengaged within the opening 75 and the turntable 30 is supported onplatform 73.

At times it may be necessary to clear debris which may collect between aturntable 30 and the hearth. This can be accomplished by the upwardextension of pistons 88 which raise plate 78 above plate 87. Raisingplate 78 results in the lifting of support platform 73 and a turntable30 to a higher position. This higher, up position can be reached onlyafter an initial up position is established by pistons 86 as indicatedin FIG. 7. Any debris collecting within the furnace may be removedtherefrom via the now more greatly exposed opening 53. This is thecondition illustrated in FIG. 8. When it is time to index another coilof rod into position to be unreeled into the forging apparatus, theplatform 73 and related mechanism are first returned to the retractedposition of FIG. 6 wherein it will be out of the way of the framestructure connected to the bottom of the hearth 36. The hearth is thenindexed into such position that another coil of rod is placed within theunreeling station and another, now empty, turntable is positioned withinthe charging station.

The lift mechanism for the charging station 28 is generally indicated at90 in FIGS. 9, and 11. This mechanism includes a support platform 91having a centering nose 92 designed to engage within the opening 75provided in the bottom of the turntable 30 and related structure. Themechanism 90 includes a first set of cylinders 93 having pistons 94 anda second set of cylinders 95 having pistons 96. The second set ofcylinders 95 is connected to frame structure 97 which is in turnconnected to the ends of the pistons 94.

The lift mechanism 90 is shown in FIG. 9 in its retracted position atwhich time the platform 91 and centering means 92 are beneath and out ofthe way of the frame structure supporting the hearth. When a coil of rodis to be charged onto a turntable located at the charging station 28,the pistons 94 are actuated so as to bring the platform 91 to theposition indicated in FIG. 10. In this figure it will be understood thatthe platform 91 has engaged the bottom of a turntable 30 and has liftedthe turntable from its original position of support on the hearth framestructure. This first position shown in FIG. 10 is to stabilize theturntable and to relieve the hearth frame structure from the shock thatoccurs when a coil of rod is deposited on a turntable.

Sometimes it becomes necessary to remove a turntable from the furnace soas to repair it or replace it with another turntable. By raising theturntable above the position shown in FIG. 10, the same mechanism whichdeposits a coil on the turntable may be used to engage beneath theturntable and thereby remove it from the furnace; this is the positionshown in FIG. 11. Thus when the pistons 96 are actuated, the supportplatform 91 is moved further upwardly so that the charger 27 may beactuated to withdraw the turntable 30 from the furnace. The mechanism isreturned to the retracted position of FIG. 9 before the hearth 36 isindexed again.

The construction of a turntable 30 is similar to that of the hearth 36in that there may be a bottom plate 98 secured beneath the refractorymaterial and above the rail-frame supports 99, see FIG. 3. Also, it willbe obvious that the lift mechanisms 72 and of FIGS. 6 through 8 and 9through 11, respectively, will be positioned at the unreeling andcharging stations 29 and 28, respectively, as generally indicated inFIG. 2.

It is believed that the foregoing constitutes a complete description ofthe rotary hearth furnace and the system for forming balls of which itis a part. It will be apparent to those skilled in the art, however,that modifications may be made in the furnace and system withoutdeparting from the scope and spirit of the invention as set forthherein.

Although the furnace and system have been de scribed with reference toparticular structures and ar' rangements, such structures andarrangements are not to constitute a limitation on the invention asclaimed except insofar as such structures and arrangements arespecifically set forth in the subjoined claims.

In a typical rotary hearth furnace constructed according to thisinvention 10 combination spindleturntables may be spaced around the mainrotary hearth. This hearth, for example, may have a diameter of 27 feetwith the spaced turntables each having a diameter of 5 feet. Eachturntable may hold up to 2500 lbs of coil. The total weight on a singleturntable does not have to be all in one coil; two 900 lb. coils, forexample, could be placed on each turntable. In the case of two-coilfeeding, the operation would begin with a first turntable in the rotaryhearth being indexed to the unreeling station for feeding the forgingapparatus. The first coil would be fed into the forging apparatus andthe second coil immediately afterwards. The hearth is then promptlyindexed again and the operation repeated. New coils may be loaded on anempty turntable at the loading station while a feeding operation takesplace.

In the operation above described, continuous production is dependentupon having sufficient capacity for heating a particular rod size. It isbelieved that changes in furnace dimension or burner size, which couldadjust the heating capacity to adapt to a different rod size, do notalter the scope and/or spirit of this invention. In any case, thefurnace of this invention makes possible a rate of feeding the forgingapparatus and, therefore, the production of grinding balls, at highspeeds not previously obtainable.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

I. A furnace for heating a plurality of coils of rod; said furnacehaving a single, unitary gas fired heating chamber; a rotary hearth forsaid chamber, said hearth having a plurality of openings therein; aspindleturntable within each said opening and clear of said hearth, eachsaid spindle-turntable being adapted to receive at least one coil of rodto be heated within said chamber; frame work located beneath said hearthso as to support same, each said spindle-turntable also resting on saidframe work; bearing means on which said frame work is engaged forpurposes of rotation; a charging station for said chamber; an unreelingstation for said chamber; and indexing means for moving said frame work,hearth and spindle-turntables so as to move a coil through substantiallyall of said chamber from said charging station to said unreelingstation.

2. The furnace of claim 1 in which a sealing means is provided betweenthe outer edge of said rotary hearth and the wall of said chamber.

3. A furnace for heating a plurality of coils of rod; said furnacehaving a single, unitary gas fired heating chamber; a rotary hearth forsaid chamber, said hearth having a plurality of openings therein; aspindleturntable within each said opening, each said spindleturntablebeing adapted to receive at least one coil of rod to be heated withinsaid chamber; frame work located beneath said hearth so as to supportsame, each said spindle-turntable also resting on said frame work;bearing means on which said frame work is engaged for purposes ofrotation; a charging station for said chamher; an unreeling station forsaid chamber; and indexing means for moving said frame work, hearth andspindle-turntable so as to move a coil through substantially all of saidchamber from said charging station to said unreeling station; andincluding a lift mechanism for said charging station, said liftmechanism being located beneath said chamber and arranged to registerwith said openings as said hearth is rotated by said indexing means,said lift mechanism having a retracted position out of the way of saidframe work, said lift mechanism having a support platform capable ofpassing through said frame work and a said opening to engage a saidspindle-turntable, and means to actuate said lift mechanism so as toengage said platform with a said spindleturntable and lift same fromsaid frame work to a first position, whereby a said coil may be placedon said so lifted spindle-turntable without shock to said frame work.

4. The furnace of claim 3 in which said actuating means may move saidplatform and spindle-turntable to a second position whereby to enablethe removal of said spindle-turntable from said chamber.

5. The furnace of claim 3 in which said platform has a centering meansthereon to register with a mating portion provided in the under side ofa said spindleturntable.

6. A furnace for heating a plurality of coils of rod; said furnacehaving a single, unitary gas fired heating chamber; a rotary hearth forsaid chamber, said hearth having a plurality of openings therein; aspindleturntable within each said opening, each said spindleturntablebeing adapted to receive at least one coil of rod to be heated withinsaid chamber; frame work located beneath said hearth so as to supportsame, each said spindle-turntable also resting on said frame work;bearing means on which said frame work is engaged for purposes ofrotation; a charging station for said chamber; an unreeling station forsaid chamber; and indexing means for moving said frame work, hearth andspindle-turntable so as to move a coil through substantially all of saidchamber from said charging station to said unreeling station; andincluding a rotary lift mechanism for said unreeling station, saidrotary lift mechanism being located beneath said chamber and arranged toregister with said openings as said hearth is rotated by said indexingmeans, said rotary lift mechanism having a retracted position out of theway of said frame work, said rotary lift mechanism having a supportmeans capable of passing through said frame work and a said opening toengage a said spindle-turntable, spindleturntable rotating meansconnected to said support means, means to actuate said rotary liftmechanism so as to engage said support means with a saidspindleturntable and lift same from said frame work to a first position,and means to actuate said rotating means so as to rotate said supportmeans when in said first position.

7. The furnace of claim 6 in which said means to actuate said rotarylift mechanism may move said support means and spindle-turntable to asecond position to ef feet a greater clearance between thespindle-turntable and said hearth whereby to enable debris to be removedfrom said chamber through a said opening.

8. The furnace of claim 6 in which said support means has a centeringmeans thereon to register with a mating portion provided in the underside of a said spindle-turntable.

9. The furnace of claim 1 including brace members fixed to the undersideof said hearth, and said frame work including an inner circular rail andan outer circular rail and cross members engaging both of said rails,and means depending from said rails and engaging said bearing means,said bearing means comprising rollers mounted on a building floor, saidhearth comprising refractory material mounted on said brace membersengaging said rails and said cross members.

10. A furnace for heating a plurality of coils of rod; said furnacehaving a single, unitary gas fired heating chamber; a rotary hearth forsaid chamber, said hearth having a plurality of openings therein; aspindleturntable within each said opening, each said spindleturntablebeing adapted to receive at least one coil of rod to be heated withinsaid chamber; frame work located beneath said hearth so as to supportsame, each said spindle-turntable also resting on said frame work;bearing means on which said frame work is engaged for purposes ofrotation; a charging station for said chamher; an unreeling station forsaid chamber; and indexing means for moving said frame work, hearth andspindle-turntable so as to move a coil through substantially all of saidchamber from said charging station to said unreeling station; and inwhich said indexing means comprises a piston-cylinder arrangement fixedto a building floor, a carriage pivotally connected to the piston, aspring biased dog protruding upwardly from said carriage, a circularindexing rail fixed to said frame work, said indexing rail beingprovided with fixed dogs protruding downwardly therefrom, and means toslidingly connect said carriage to said rail so that said spring biaseddog will engage said fixed dogs, whereby movement of the piston in onedirection will effect engagement of said spring biased dog with a saidfixed dog so as to move said hearth a given increment and move ment ofsaid piston in the opposite direction will result in said spring biaseddog passing beneath the next fixed dog so as to be in position to engagethis last mentioned dog upon next actuation of the piston.

11. The furnace of claim 1 in which a said spindleturntable comprisesrefractory material having a plate fixed to the underside thereof, andbrace members fixed to said plate.

12. A furnace for heating a plurality of coils of rod; said furnacehaving a single, unitary gas fired heating chamber; a rotary hearth forsaid chamber, said hearth having a plurality of openings therein; aspindleturntable within each said opening, each said spindleturntablebeing adapted to receive at least one coil of rod to be heated withinsaid chamber; frame work located beneath said hearth so as to supportsame, each said spindle-turntable also resting on said frame work;bearing means on which said frame work is engaged for purposes ofrotation; a charging station for said chamher; an unreeling station forsaid chamber; and indexing means for moving said frame work, hearth andspindle-turntable so as to move a coil through substantially all of saidchamber from said charging station to said unreeling station; andincluding a sealing means provided between the outer edge of said rotaryhearth and the wall of said chamber; said sealing means comprising acircular channel member mounted on one of said wall and said hearth anda circular rim mounted on the other of said wall and said hearth andengaged within said channel member.

13. A furnace for heating a plurality of coils of rod; said furnacehaving a single, unitary gas fired heating chamber; a rotary hearth forsaid chamber, said hearth having a plurality of openings therein; aspindle turntable within each said opening, each said spindleturntablebeing adapted to receive at least one coil of rod to be heated withinsaid chamber; frame work located beneath said hearth so as to supportsame, each said spindle-turntable also resting on said frame work;bearing means on which said frame work is engaged for purposes ofrotation; a charging station for said chamber; an unreeling station forsaid chamber; and indexing means for moving said frame work, hearth andspindle-turntable so as to move a coil through substantially all of saidchamber from said charging station to said unreeling station; andincluding a sealing means provided between the outer edge of said rotaryhearth and the wall of said chamber; said sealing means comprising afirst L-shaped bracket fixed to said hearth, a second L-shaped bracketfixed to said chamber wall, and a J shaped member swingably hanging fromsaid second L-shaped bracket and adapted to abut said first L- shapedbracket, whereby temperature of said furnace is maintained whileallowing debris and scale to escape.

14. The furnace of claim 1 in which said openings are evenly spacedabout said hearth, the spacing being such that when one said opening isat the said charging station and another of said openings is at the saidunreeling station there will be only one opening located between thosesides of said stations which are closest together and a plurality ofopenings between those sides of said stations which are farthest apart.

15. A furnace for heating a plurality of coils of rod; said furnacehaving a single, unitary gas fired heating chamber lined with refractorymaterial; a circular, rotary hearth for said chamber, said hearthcomprising a plate having refractory material located thereon, firstbrace members fixed to the underside of said plate, said plate andmaterial having a plurality of evenly spaced, circular openings locatedtherethrough between said first brace members and disposed in circularfashion; a circular spindle-turntable within each said opening out ofcontact with said hearth, each said spindle-turntable being adapted toreceive at least one coil of rod to be heated within said chamber, eachsaid spindleturntable comprising a plate with refractory materialthereon and second brace members fixed to the underside of said plate;frame work comprising an annular inner rail and an annular outer railand cross members joining said rails, and means depending from saidrails and engaging rollers mounted on a building floor; said hearth andsaid spindle-turntables resting on said frame work; a charging stationfor said chamber, lift mechanism having a platform normally retractedbeneath said station and adapted to be moved through said frame work anda said opening to engage a spindle-turntable and move it from engagementwith said frame work, and actuating means to move said platform intoengagement with a said spindle-turntable to lift it from said frame workwhereby a said coil may be placed thereon without shock to said framework; an unreeling station for said chamber, rotary and lift mechanismhaving a support means normally retracted beneath said unreeling stationand adapted to be moved through said frame work and a said opening toengage a spindleturntable and move it from engagement with said framework, second actuating means to move said support means into engagementwith a said spindle-turntable to lift it from said frame work, androtating means to rotate said support means when in its last mentionedposition; and indexing means for moving said frame work, hearth andturntables so as to move a said coil from said charging station, throughsubstantially all of said chamber, to said unreeling station, saidindexing means including an annular indexing rail fixed to said framework, said indexing rail having a series of evenly spaced dogs dependingtherefrom throughout, and pistoncylinder means mounted on the buildingfloor and having a carriage adapted to move along said indexing rail,said carriage having a member to engage successive of said dogs uponreciprocation of the piston-cylinder means whereby to move said framework in step by step fashion,

16. A gas fired furnace comprising a single, unitary cylindrical heatingchamber; a rotatable, circular hearth for said chamber; a plurality ofspindleturntables evenly spaced throughout said hearth and clearthereof; means to rotate said hearth; and selective means to engage asaid spindle-turntable when said hearth has been rotated to bring suchturntable to said selective means, whereby a said spindle-turntable maybe raised with respect to said hearth.

1. A furnace for heating a plurality of coils of rod; said furnacehaving a single, unitary gas fired heating chamber; a rotary hearth forsaid chamber, said hearth having a plurality of openings therein; aspindle-turntable within each said opening and clear of said hearth,each said spindle-turntable being adapted to receive at least one coilof rod to be heated within said chamber; frame work located beneath saidhearth so as to support same, each said spindle-turntable also restingon said frame work; bearing means on which said frame work is engagedfor purposes of rotation; a charging station for said chamber; anunreeling station for said chamber; and indexing means for moving saidframe work, hearth and spindle-turntables so as to move a coil throughsubstantially all of said chamber from said charging station to saidunreeling station.
 2. The furnace of claim 1 in which a sealing means isprovided between the outer edge of said rotary hearth and the wall ofsaid chamber.
 3. A furnace for heating a plurality of coils of rod; saidfurnace having a single, unitary gas fired heating chamber; a rotaryhearth for said chamber, said hearth having a plurality of openingstherein; a spindle-turntable within each said opening, each saidspindle-turntable being adapted to receive at least one coil of rod tobe heated within said chamber; frame work located beneath said hearth soas to support same, each said spindle-turntable also resting on saidframe work; bearing means on which said frame work is engaged forpurposes of rotation; a charging station for said chamber; an unreelingstation for said chamber; and indexing means for moving said frame work,hearth and spindle-turntable so as to move a coil through substantiallyall of said chamber from said charging station to said unreelingstation; and including a lift mechanism for said charging station, saidlift mechanism being located beneath said chamber and arranged toregister with said openings as said hearth is rotated by said indexingmeans, said lift mechanism having a retracted position out of the way ofsaid frame work, said lift mechanism having a support platform capableof passing through said frame work and a said opening to engage a saidspindle-turntable, and means to actuate said lift mechanism so as toengage said platform with a said spindle-turntable and lift same fromsaid frame work to a first position, whereby a said coil may be placedon said so lifted spindle-turntable without shock to said frame work. 4.The furnace of claim 3 in which said actuating means may move saidplatform and spindle-turntable to a second position whereby to enablethe removal of said spindle-turntable from said chamber.
 5. The furnaceof claim 3 in which said platform has a centering means thereon toregister with a mating portion provided in the under side of a saidspindle-turntable.
 6. A furnace for heating a plurality of coils of rod;said furnace having a single, unitary gas fired heating chamber; arotary hearth for said chamber, said hearth having a plurality ofopenings therein; a spindle-turntable within each said opening, eachsaid spindle-turntable being adapted to receive at least one coil of rodto be heated within said chamber; frame work located beneath said hearthso as to support same, each said spindle-turntable also resting on saidframe work; bearing means on which said frame work is engaged forpurposes of rotation; a charging station for said chamber; an unreelingstation for said chamber; and indexing means for moving said frame work,hearth and spindle-turntable so as to move a coil through substantiallyall of said chamber from said charging station to said unreelingstation; and including a rotary lift mechanism for said unreelingstation, said rotary lift mechanism being located beneath said chamberand arranged to register with said openings as said hearth is rotated bysaid indexing means, said rotary lift mechanism having a retractedposition out of the way of said frame work, said rotary lift mechanismhaving a support means capable of passing through said frame work and asaid opening to engage a said spindle-turntable, spindle-turntablerotating means connected to said support means, means to actuate saidrotary lift mechanism so as to engage said support means with a saidspindle-turntable and lift same from said frame work to a firstposition, and means to actuate said rotating means so as to rotate saidsupport means when in said first position.
 7. The furnace of claim 6 inwhich said means to actuate said rotary lift mechanism may move saidsupport means and spindle-turntable to a second position to effect agreater clearance between the spindle-turntable and said hearth wherebyto enable debris to be removed from said chamber through a said opening.8. The furnace of claim 6 in which said support means has a centeringmeans thereon to register with a mating portion provided in the underside of a said spindle-turntable.
 9. The furnace of claim 1 includingbrace members fixed to the underside of said hearth, and said frame workincluding an inner circular rail and an outer circular rail and crossmembers engaging both of said rails, and means depending from said railsand engaging said bearing means, said bearing means comprising rollersmounted on a building floor, said hearth comprising refractory materialmounted on said brace members engaging said rails and said crossmembers.
 10. A furnace for heating a plurality of coils of rod; saidfurnace having a single, unitary gas fired heating chamber; a rotaryhearth for said chamber, said hearth having a plurality of openingstherein; a spindle-turntable within each said opening, each saidspindle-turntable being adapted to receive at least one coil of rod tobe heated within said chamber; frame work located beneath said hearth soas to support same, each said spindle-turntable also resting on saidframe work; bearing means on which said frame work is engaged forpurposes of rotation; a charging station for said chamber; an unreelingstation for said chamber; and indexing means for moving said frame work,hearth and spindle-turntable so as to move a coil through substantiallyall of said chamber from said charging station to said unreelingstation; and in which said indexing means comprises a piston-cylinderarrangement fixed to a building floor, a carriage pivotally connected tothe piston, a spring biased dog protruding upwardly from said carriage,a circular indexing rail fixed to said frame work, said indexing railbeing provided with fixed dogs protruding downwardly therefrom, andmeans to sliDingly connect said carriage to said rail so that saidspring biased dog will engage said fixed dogs, whereby movement of thepiston in one direction will effect engagement of said spring biased dogwith a said fixed dog so as to move said hearth a given increment andmovement of said piston in the opposite direction will result in saidspring biased dog passing beneath the next fixed dog so as to be inposition to engage this last mentioned dog upon next actuation of thepiston.
 11. The furnace of claim 1 in which a said spindle-turntablecomprises refractory material having a plate fixed to the undersidethereof, and brace members fixed to said plate.
 12. A furnace forheating a plurality of coils of rod; said furnace having a single,unitary gas fired heating chamber; a rotary hearth for said chamber,said hearth having a plurality of openings therein; a spindle-turntablewithin each said opening, each said spindle-turntable being adapted toreceive at least one coil of rod to be heated within said chamber; framework located beneath said hearth so as to support same, each saidspindle-turntable also resting on said frame work; bearing means onwhich said frame work is engaged for purposes of rotation; a chargingstation for said chamber; an unreeling station for said chamber; andindexing means for moving said frame work, hearth and spindle-turntableso as to move a coil through substantially all of said chamber from saidcharging station to said unreeling station; and including a sealingmeans provided between the outer edge of said rotary hearth and the wallof said chamber; said sealing means comprising a circular channel membermounted on one of said wall and said hearth and a circular rim mountedon the other of said wall and said hearth and engaged within saidchannel member.
 13. A furnace for heating a plurality of coils of rod;said furnace having a single, unitary gas fired heating chamber; arotary hearth for said chamber, said hearth having a plurality ofopenings therein; a spindle-turntable within each said opening, eachsaid spindle-turntable being adapted to receive at least one coil of rodto be heated within said chamber; frame work located beneath said hearthso as to support same, each said spindle-turntable also resting on saidframe work; bearing means on which said frame work is engaged forpurposes of rotation; a charging station for said chamber; an unreelingstation for said chamber; and indexing means for moving said frame work,hearth and spindle-turntable so as to move a coil through substantiallyall of said chamber from said charging station to said unreelingstation; and including a sealing means provided between the outer edgeof said rotary hearth and the wall of said chamber; said sealing meanscomprising a first L-shaped bracket fixed to said hearth, a secondL-shaped bracket fixed to said chamber wall, and a J-shaped memberswingably hanging from said second L-shaped bracket and adapted to abutsaid first L-shaped bracket, whereby temperature of said furnace ismaintained while allowing debris and scale to escape.
 14. The furnace ofclaim 1 in which said openings are evenly spaced about said hearth, thespacing being such that when one said opening is at the said chargingstation and another of said openings is at the said unreeling stationthere will be only one opening located between those sides of saidstations which are closest together and a plurality of openings betweenthose sides of said stations which are farthest apart.
 15. A furnace forheating a plurality of coils of rod; said furnace having a single,unitary gas fired heating chamber lined with refractory material; acircular, rotary hearth for said chamber, said hearth comprising a platehaving refractory material located thereon, first brace members fixed tothe underside of said plate, said plate and material having a pluralityof evenly spaced, circular openings located therethrough between saidfirst brace members and disposed in circuLar fashion; a circularspindle-turntable within each said opening out of contact with saidhearth, each said spindle-turntable being adapted to receive at leastone coil of rod to be heated within said chamber, each saidspindle-turntable comprising a plate with refractory material thereonand second brace members fixed to the underside of said plate; framework comprising an annular inner rail and an annular outer rail andcross members joining said rails, and means depending from said railsand engaging rollers mounted on a building floor; said hearth and saidspindle-turntables resting on said frame work; a charging station forsaid chamber, lift mechanism having a platform normally retractedbeneath said station and adapted to be moved through said frame work anda said opening to engage a spindle-turntable and move it from engagementwith said frame work, and actuating means to move said platform intoengagement with a said spindle-turntable to lift it from said frame workwhereby a said coil may be placed thereon without shock to said framework; an unreeling station for said chamber, rotary and lift mechanismhaving a support means normally retracted beneath said unreeling stationand adapted to be moved through said frame work and a said opening toengage a spindle-turntable and move it from engagement with said framework, second actuating means to move said support means into engagementwith a said spindle-turntable to lift it from said frame work, androtating means to rotate said support means when in its last mentionedposition; and indexing means for moving said frame work, hearth andturntables so as to move a said coil from said charging station, throughsubstantially all of said chamber, to said unreeling station, saidindexing means including an annular indexing rail fixed to said framework, said indexing rail having a series of evenly spaced dogs dependingtherefrom throughout, and piston-cylinder means mounted on the buildingfloor and having a carriage adapted to move along said indexing rail,said carriage having a member to engage successive of said dogs uponreciprocation of the piston-cylinder means whereby to move said framework in step by step fashion.
 16. A gas fired furnace comprising asingle, unitary cylindrical heating chamber; a rotatable, circularhearth for said chamber; a plurality of spindle-turntables evenly spacedthroughout said hearth and clear thereof; means to rotate said hearth;and selective means to engage a said spindle-turntable when said hearthhas been rotated to bring such turntable to said selective means,whereby a said spindle-turntable may be raised with respect to saidhearth.